This invention relates to a household electronic toaster and a method of manufacturing the same, but aspects of this invention can be used in other heating appliances, particularly toasters for commercial use.
Household toasters commonly have a housing confining a toasting chamber and heating elements within the toasting chamber between which a pair of bread support arms are vertically-movable between a lowered position for toasting bread or other food items to a raised position for permitting the bread or other food items to be placed on or removed from the bread support arms.
Some toasters have only one bread support arm and some have more than two bread support arms. For ease of discussion, this invention is disclosed for use in the toaster configuration which has two bread supports, such presently being the most common configuration. However, as will become apparent, several aspects of this invention described below can be used in other toaster configurations.
A pair of wire grills located on each side of each bread support prevent the food items being toasted from engaging the heating elements. One or both of the wire grills of each pair may be movable toward the other grill and into engagement with the food items as the bread support arms are lowered into the toasting chamber to closely confine the food items in a substantially predetermined position between the heating elements.
In many toasters, the bread support arms are part of a vertically movable support carriage to which the bread supports are connected. Spring means biases the support carriage upwardly so that the bread support arms are normally in their upper, non-toasting position. The support carriage can be lowered to the toasting position by manipulation of a control lever accessible from outside the housing. During a toasting cycle, a latch mechanism holds the support carriage with its bread support arms in their lowered, toasting position. User-adjustable electric or electronic means controls the toasting cycle times during which the bread support arms are latched in their lowered position in order to toast the food items to the desired toast color.
Toasters are often so designed that the support carriage, as it moves down into its latched, toasting position, engages and closes a normally open power switch in a circuit that provides electrical power to the heating elements. The power switch opens as the support carriage subsequently moves upwardly. A hazardous condition can be created if a food item being toasted sticks to the wire grills and prevents the bread support carriage from completing its upward movement and the power switch fails to open. Various constructions have been proposed to ensure that the power to the heating elements is interrupted at or shortly after the end of a toasting cycle even if the bread support carriage does not move upwardly.
The several mechanical and electrical or electronic components derive support from a frame covered by a cover or housing. To provide for convenient removal of bread crumbs or other waste dropping from the food items being toasted, a crumb tray is often pivotally mounted on the base member of the frame.
Notwithstanding the several elements that comprise a household toaster, household toasters are usually remarkably inexpensive. The low cost partly results from the use of sophisticated manufacturing and assembling techniques. There is, however, an ever-present need to improve upon the quality of toasters and the manufacturing and assembling operations used to produce toasters.
An object of this invention is to provide an improved household electronic toaster and a method for manufacturing the same. More particularly, an object of this invention is to provide a rugged, high quality household toaster which can be manufactured at relatively low cost. To accomplish these objects, this invention utilizes improvements in several areas of toaster construction and operation.
A toaster made in accordance with this invention comprises an electronic circuit including an application specific integrated circuit, commonly called an ASIC, mounted chip-on-board on a printed circuit board, to control the operation of toaster heating elements and an electromagnet to which relatively high voltage is applied to hold an armature carried by a bread carriage and toaster-operating assembly.
In another aspect of this invention, the armature is freely suspended from the bread carriage and toaster-operating assembly and accurately guided onto the electromagnet when the bread carriage is lowered.
In yet another aspect of this invention, the toaster has a one-piece main frame that includes both a base frame plate and a rear frame plate and several economies are obtained by virtue of the construction of the toaster.
In still another aspect of this invention, a one-piece control support member is mounted on the base frame plate that supports both mechanical and electronic assemblies for controlling the operation of the toaster in predetermined relative positions.
In another aspect of this invention, an armature used to hold the bread carriage in a lowered position for toasting is accurately guided into engagement with an electromagnet to assure that the armature will be strongly held by the electromagnet.
In another aspect of this invention, the electromagnet is mounted on a printed circuit board and the armature is loosely suspended from a support housing, the support housing having cam surfaces engaging the printed circuit board as the armature is lowered to assure proper alignment of the armature with the electromagnet.
In a still further aspect of this invention, the armature support housing has switch contact-engaging surfaces that close power switches as the armature and the bread carriage are lowered together.
In a related aspect of this invention, the support housing and the armature can move upwardly relative to the bread carriage if the bread carriage accidentally becomes stuck so that the power switches will assuredly be opened at the end of a toasting cycle.
In a related aspect of this invention, the cam surfaces are supported on plates that provide a barrier between live electricity and the toaster housing or cover.
In a further aspect of this invention, a unique crumb tray mounting arrangement is provided whereby a crumb tray may be mounted on the base frame member without the use of additional parts or tools.